Method of producing electrothermal filament containing carbon black and the product of the method

ABSTRACT

A method of producing electrothermal filament containing carbon black that first grafts carbon black to monomer to form grafted copolymer. Then, the grafted copolymer is coated around the filament to form a conductive core. Lastly, membrane is laminated around the conductive core to protect and insulate the core.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of producingelectrothermal filament and the electrothermal filaments themselves, andmore particularly a method of producing electrothermal filamentcontaining carbon black by a grafting technique and the electrothermalfilament containing carbon black.

[0003] 2. Description of Related Art

[0004] Since so many improvements have taken place in the textile field,cloth has to have more features to attract consumers. Multiple featuressuch as waterproofing or heat retention are added to finished cloth. Howto make cloth retain heat is a special and valuable feature to textilemanufacturers.

[0005] Numerous electrically conductive fibers with unstable electricalproperties have been developed. Most of them are cloth combined withconductive media such as conductive filaments, conductive plates orsemi-conductive membranes. However, the resultant cloth incorporating aconductive media is very heavy and inflexible so that the cloth isinconvenient to carry and handle and is hard to tailor to a desiredshape. Although the cloth with conductive membrane has better resilientthan other cloth with other conductive media, the cloth with conductivemembrane still do not have water-proof efficiency and easilydeteriorates after laundering and no longer conducts electricity. Otherelectrically conductive fibers are made by plating a metal layer on thesurface of a non-conductive fiber or by formation of an electricallyconductive coating layer on a fiber from resin or rubber in whichelectrically-conductive carbon black is incorporated. Drawbacks aretheir complex and difficult production processes or their easy loss ofelectrical conductivity during clearing involving chemical treatment andin actual use involving wear and repeated washing.

[0006] The present invention has arisen to mitigate and/or obviate thedisadvantages of the conventional electrically conductive fiber.

SUMMARY OF THE INVENTION

[0007] The main objective of the present invention is to provide amethod of producing electrothermal filament containing carbon black thatproduces electrically conductive filaments having excellent resilienceand durable electrical conductivity even after repeated laundering.

[0008] Further benefits and advantages of the present invention willbecome apparent after a careful reading of the detailed description withappropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a block diagram of a method of producing electrothermalfilaments containing carbon black in accordance with the presentinvention;

[0010]FIG. 2 is a schematic diagram of the method in FIG. 1 beingcarried out; and

[0011]FIG. 3 is a cross-sectional side plan view of an electrothermalfilament containing carbon black in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0012] With reference to FIG. 1, a method of producing an electrothermalfilament containing carbon black in accordance with the presentinvention comprising the acts of obtaining the materials, graftingcarbon black to monomers to form grafted copolymers, coating a filamentwith the grafted copolymers, laminating a membrane on the filament andattaching two electrodes to each electrothermal filament.

[0013] The material that must be obtained to perform the method ofproducing an electrothermal filament containing carbon black consists ofmicro-powder carbon black, a grafting monomer, an initiator, aterminating agent, nitrogen gas and rolls of a membrane. Carbon black ismicro-particles and is conductive material. The grafting monomer isstyrene, and the initiator contains 0.5˜2% benzoyl peroxide. Theterminating agent is acetone. The membrane is a soft, flexible materialsuch as a polyethylene (PE) or thermoplastic urethane (TPU) elastomer.

[0014] To graft the carbon black to a monomer, the carbon black is mixedwith a grafting monomer and an initiator. Carbon black and styrene arerespectively 8˜15% and 80˜90% with the residual proportion being theinitiator. At the end of the grafting step, the terminating agent isadded to the mixture of carbon black and the monomer to stop thegrafting reaction.

[0015] The carbon black, grafting monomer (styrene) and the initiator(benzoyl peroxide) are mixed in a reaction tank to form a graftedcopolymer. Then, nitrogen gas is guided into the reaction tank tomaintain the temperature of mixture in the tank at 60° C. The graftingreaction takes 6˜8 hours. At the end of the grafting reaction, theterminating agent (acetone) is added to the reaction tank to stop thegrafting reaction thereby controlling the quantity of carbon black inthe grafted copolymer. Consequently, the quality of the graftedcopolymer is controlled and stable. The grafting reaction is depicted inthe following chemical reaction: Carbon black+C₆H₅—(C₂H₂) 60° C. for 6˜8hr carbon black-(C₂H₂)—C₆H₅

[0016] According to this reaction, the carbon black is grafted withmonomer by free radicals of the carbon black to coat a layer of monomeraround outer periphery of the carbon black micro-particles. Whereby,each carbon black micro-particle repulse others to avoid coagulationbetween carbon black micro-particles.

[0017] To coat filaments with grafted copolymer, filaments are passedthrough the grafted copolymer to coat the filaments with a layercontaining carbon black. With reference to FIG. 2, the filament (10)wound on a spindle (101) is reeved around rollers (12) through graftedcopolymer (20) in a first tank (11). When the filament (10) passesthrough the grafted copolymer (20) in the first soaking tank (11), thegrafted copolymer (20) permeates and coats the filament (10). After thefilament (10) leaves the grafted copolymer (20) in the first tank (11),a pair of rollers (12) squeegees excess grafted copolymer (20) from thefilament (10). Then the filament (10) is passed through graftedcopolymer (20) in a second tank (13) and a third tank (15) to increasethe thickness of the grafted copolymer on the filament (10) to ensurethat sufficient the carbon black is on the filament (10). After coatingthe filament (10) with the grafted copolymer (20), the filament (10) isdelivered to a curing roller assembly (17) to completely cure thegrafted copolymer on the filament (10).

[0018] After curing the grafted copolymer on the filament, two sheets ofa membrane (25) are respectively delivered from two membrane spindles(18) respectively mounted on opposite sides of the filament (10). Themembranes (25) are laminated on the filament (10) by a pair ofcompressing wheels (181). The membrane (25) on the filament (10) keepsthe carbon black from easily coming off the filament (10) and providesan insulating layer to complete the electrothermal filament. Lastly, theelectrothermal filaments are winded up on a final roller (19).

[0019] With reference to FIG. 3, each electrothermal filament (30) iscomposed of a conductive core (21) of grafted copolymer and a membrane(25) surrounding around the core (21). The conductive core (21) has twoends projecting out of the membrane (25), and two electrodes (35) arerespectively attached to opposite ends of the conductive core (21). Theelectrothermal filament (30) generates heat when current passes throughthe conductive core (21).

[0020] Based on the foregoing description, the electrothermal filamentcontaining carbon black and the method of producing said filament havethe following advantages:

[0021] 1. Because the carbon black is grafted with grafting monomer, thecarbon black has polarization to cause repulsion effect after graftingwith the monomer and then is evenly distributed when coated on thefilament. Therefore, the electrothermal filament uses less carbon blackbut has excellent conductivity to evenly heat the electrothermalfilament.

[0022] 2. The soft and flexible membrane coating around the conductivecore encloses the carbon black inside to prevent the carbon black fromseparating from the filament during washing. Additionally, theflexibility of the electrothermal filament is improved after laminatingthe membrane.

[0023] 3. The electrothermal filament using carbon black to form theconductive core is light and efficiently generates heat. Therefore, thecloth made of the electrothermal filament is light-weight and hasexcellent warming features during use.

[0024] Although the invention has been explained in relation to itspreferred embodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thespirit and scope of the invention as hereinafter claimed.

What is claimed is:
 1. A method of producing electrothermal filamentcontaining carbon black, the method comprising following acts: obtainingcarbon black, a grafting monomer, an initiator, a terminating agent,nitrogen gas and rolls of a membrane; grafting the carbon black withmonomers by mixing the carbon black with the grafting monomer andinitiator to graft the carbon black to the monomer to form graftedcopolymers and then adding a terminating agent to the mixture to stopthe grafting; coating the filaments with the grafted copolymers bypassing the filaments through the grafted copolymers to apply a layer ofcarbon black on the filaments; and laminating membranes on the filament.2. The method of producing electrothermal filament containing carbonblack as claimed in claim 1, wherein the monomer is styrene; theinitiatior is a 0.5˜2% benzoyl peroxide solution; the terminating agentis acetone; the membranes are soft and flexible material selected fromthe group comprising polyethylene (PE) or thermoplastic urethane (TPU)elastomer; and the carbon black proportion is 8˜15%; the styrene monomeris 80˜90%; and the remaining component is benzoyl peroxide solution. 3.The method of producing electrothermal filament containing carbon blackas claimed in claim 2, wherein the carbon black, styrene monomer, andbenzoyl peroxide are mixed to form a grafted copolymer; wherein nitrogengas is added to maintain a temperature of 60° F. for 6 to 8 hours. 4.The method of producing electrothermal filament containing carbon blackas claimed in claim 1, where the act of coating the filaments with thegrafted copolymer comprises passing the filament through the graftedcopolymer three times to ensure sufficient carbon black is on thefilament.
 5. The method of producing electrothermal filament containingcarbon black as claimed in claim 1 further comprising the act ofrespectively attaching two electrodes to opposite ends of eachelectrothermal filament.
 6. An electrothermal filament in accordancewith the present invention comprising: grafted copolymer formed bygrafting carbon black to a monomer; a filament having two ends coatedwith the grafted copolymer; and a membrane laminated on the filamenthaving the grafted copolymer as insulation.
 7. The electrothermalfilament as claimed in claim 6, wherein the electrothermal filamentfurther has two electrodes respectively attached to opposite ends of theelectrothermal filament.